This invention relates to a method and apparatus for controlling a tool magazine storing a plurality of tools used in combination with a machine tool and an automatic tool exchange device, and more particularly a method and apparatus for controlling a tool magazine capable of indexing a designated one of the tools to be used next time to a tool exchange position with a minimum travel or rotation of the tool magazine.
Typical prior art methods and apparatuses for controlling a tool magazine of this type are as follows:
1. A data control system disclosed in U.S. Pat. No. 3,173,204, dated Mar. 16, 1965.
This data control system comprises a plurality of individual record members that are associated with respective tool storage locations in the storage station. Each record member affords a record medium for registering code data identifying an individual tool. Sensing means are provided for sensing the code data recorded on the record members. Means are also provided for clearing the code data from a record member upon removal of the associated tool from the storage station. The code data identifying a tool are stored in a separate data storage means as long as the tool is separated from the tool storage station. The system also includes means coupled to the aforementioned data storage means for automatically recording the identifying code data for a given tool on one of the record members upon transfer of the tool to the storage location that is associated with that record member. Control means are also provided for actuating the transfer means of the machine to transfer selected tools between the storage and work stations, and these control means are coupled to and controlled by the sensing means.
2. An automatic tool searching apparatus as disclosed in Japanese Patent Publication No. 179/81 wherein the pot numbers of a tool magazine and tool numbers received in respective tool pots are sequentially stored in a memory device in an order determined by taking the tool exchange position as a reference, first scanning means which scans the memory device in a direction in which the tool number increases and second scanning means which scans the memory device in a direction in which the tool number decreases are operated alternately, and the results of scannings are sequentially compared with the number of the tool to be used next time. Further, rotation direction judging means is provided which judges the direction of rotation of the tool magazine according to either one of the output signals of the first and second scanning means when a coincidence is obtained.
According to the first prior art reference, the tool magazine is rotated always in the definite direction so that for the purpose of indexing a designated tool in a tool pot located most remotely from the tool exchange position the tool magazine must be rotated about 360.degree., thus requiring a longer time for indexing. More particularly, it cannot realize the feature of short travel.
In contrast, although the second prior art reference has the short travel performance, it is essential to provide a comparator for detecting the coincidence so that the circuit construction becomes complicated.